The Creativity Production Index - the average number of spots produced by a sample of agency offices - dipped again slightly in September, marking the third straight month of declines. The September index of 13.9 still outpaces a year ago, however, and after three quarters the 2003 CPI is three points ahead of 2002. In Los Angeles, on the other hand, commercials production days fell again in September following two months of year-to-year gains. The L.A. Film Office clocked 364 location shooting days in September, down nearly 30 percent from a year ago, returning to a downward trend that has dominated the year. After posting positive gains in only three months - March, July and August - L.A.'s commercials production totals entered the fourth quarter lagging behind 2002's pace by 4 percent.